Don,
In spite of all my comments favorable to Tilapia, and they have many, many wonderful attributes, I do not believe I would stock them if they survived year around....that would be a tough decision.
Last fall, as the temps first began cooling, I observed a school of 6 to 12 inch Tilapia just milling around just below the surface. I would conservately estimate 200 fish in that school. Frankly, it frightened me thinking that I was headed to a massive fish kill when the water temps dropped. It did not happen. The HSB, by observation, litterally slaughtered the Tilapia as they became somewhat lethargic with declining temps.
After the die-off happened, I found very few, less than half a dozen of dead Tilapia. My conclusion is that they were all consumed by HSB and LMB.
In a pond with no predators, I saw a massive fish kill of small Tilapia.
Don, I wrote a paper summarizing all this and would be happy to send it to you (or anyone) if interested.
My research has taken me to articles about the lakes in Mexico where Tilapia do survive year around. In summary, they have found excellent LMB fishing in lakes that also receive heavy netting pressures on Tilapia...lakes without that continual harvesting of Tilapia have had problems with LMB fry survival.
Okay, I could go on and on, but to answer your question more directly...if I had a pond with year around surviving Tilapia, I would keep every one of them caught and would probably even set up traps or nets to catch others. Don, we are talking about a fish that reproduces like crazy. Its great in a controlled environment, e.g. winter kill, but something to be cautious about in an uncontroled environment.
p.s. if you are not seeing them, then I would say you must have an excellent predator population. I see them regularly, small, medium, and large as the season goes on.
p.s.s the paper is on its way...check your e-mail
